"They still want information out of the two people that were arrested," said Brad Garrett, former FBI agent and ABC News consultant. "They don't want to compromise that until they get all of the information."

Arnold, a married mother of two and stepmother of three, disappeared last Saturday around 6:30 a.m. while jogging near her home in Sidney, Mont. A single running shoe was the only trace left behind.

Hundreds of community members turned out to help the Sidney Police Department and the FBI search for Arnold, who was a beloved math teacher at Sidney Public School. But it was an anonymous call to a tip line that gave investigators the break they needed.

One of the two men arrested is a 47-year-old man being held in nearby Williston, N.D. The other is a 22-year-old man found several miles away in Rapid City, S.D. Authorities have not revealed whether Arnold was targeted or the victim of a hit-and-run.

"The scary thing is it maybe just be random," said Garrett. "It may be that she was hit by accident, or that she was abducted."

Arnold's friends and family gathered to remember her at a memorial service Friday night.

"We would like to thank police, FBI, people of Sidney, the people around who have turned out to help, and the role they played in bringing Sherry back home," Arnold's husband, Gary Arnold, told ABC News. "It wasn't how we wanted her to come home, but she came home to us."

Sidney, a small town of roughly 5,000 people, has experienced an influx of out-of-town oil workers following the Bakken oil boom in North Dakota. Crime rates in the area have also swelled, with a rise in bar fights, domestic violence and drunk driving.

"We own the day, they own the night," Sidney Mayor Bret Smelser said of the oil workers and the increase in crime. "Unfortunately, Sherry was running in the early hours of the morning."